A new electrochemical three-component annulation−iodosulfonylation of 1,5-enyne-containing para-quinone methides (p-QMs) has been established by using available arylsulfonyl hydrazides and potassium iodide under environmentally benign conditions. The electrosynthesis offers sustainable and efficient access to construct spirocyclohexadienone-containing (E)indenes without any additional catalyst or oxidant through a sulfonyl-radical-triggered 1,6-addition and an I + -mediated ipsocyclization cascade. Notably, potassium iodide plays the triple role of an electrolyte, a redox catalyst, as well as an iodination reagent.
A general asymmetric deconstructive alkynylation of cyclic oximes with terminal alkynes was reported using copper/ chiral cinchona alkaloid-based N,N,P-ligand catalysts and used to produce more than 60 examples of enantioenriched γand δalkynyl nitriles in a highly functional group-compatible manner. A wide variety of low-cost terminal alkynes and easily available cyclic oximes with substituent diversity were found to be well tolerated with the current asymmetric transformation with good functional group tolerance. The resulting chiral alkynyl nitriles are intermediates, which could be converted into skeletally diverse chiral molecules, including δ-alkynyl amides, ε-alkenyl carbamate, and ζ-keto nitrile, under suitable reaction conditions.
Two classes of new catalytic spiroannulationfluormethylfunctionaliztions of para-quinone methide (p-QM)-containing 1,5-enynes have been established under redox-neutral conditions. Palladium-catalyzed spiroannulation-iododifluoromethylation with ethyl difluoroiodoacetate oriented completely stereoselective access to (Z)-spiroindenes and the latter included copper-catalyzed threecomponent spiroannulation-cyanotrifluoromethylation starting from Togni's reagent and trimethylsilanecarbonitrile (TMSCN). Both reaction pathways involve fluoroalkyl radicaltriggered 1,6-addition/5-exo-dig annulation/metal radical cross-coupling/reductive elimination sequence, providing practical and stereoselective protocols for rapidly constructing cyclohexadienone-containing spiroindenes with generally good yields.
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